EP, shaping in form when conductive parts relating to vacuum interrupter and circuit breaker are simultaneously inserted into solid insulating materials which easily solidified like epoxy resin, is used to control switchgears. GIS RMU, using SF6 as insulating medium, tends to be obsolete for its toxicity against environmental requirements. Thus, there is a thriving development of new solid insulating, gas insulating, and composite insulating switchgears and devices. Among these devices, there are various structures for 3-position switchgears. For instance, vacuum tubes and VI components are embedded in a same insulating pole, while the cost of vacuum tube is pretty high. Other ways, neither rotary 3-position disconnectors composite with EP nor direct-driving 3-position disconnectors composite with EP, despite of the enhancing design in structures, have limits in miniaturization for high voltage electrical devices. Besides, putting two different components together has difficulties in coherence and has a heavy load of assembling work.
Just as published on the Chinese Patent Document, whose authorized announcement number is CN203434515U, on Feb. 12, 2014, the patent is called Disconnector and Circuit Breaker Composite Electrical Apparatus for GIS. It consists of CB operating mechanism, disconnector operating mechanism, EP, sealing plate, main loop and transmission mechanism of disconnector. CB operating mechanism and disconnector operating mechanism are integral in structures and fixed on one side of the sealing aluminum plate, and EP and the main loop of disconnector are fastened on the other side. The scheme mentioned above makes the whole structure more compact and also smaller in volume. However, it is obvious that the separate design of 3-position mechanism and EP takes a lot room and makes assembly cumbersome. Therefore, it is necessary to improve the existing EP.